With kinds of services using a wireless mobile communication system being greatly diversifying, new technologies to effectively support such services have been required and thus many studies and developments therefor have been made in the wireless mobile communication system.
Device-to-device (D2D) communication is one of new technologies for the solution to new services. Basically, D2D communication allows a certain device to directly communicate with any other neighboring device. Using such D2D communication technology, the device can perform a discovery function to find neighboring devices and a direct communication function with such devices.
Compared with traditional communication using a base station in the existing wireless network, D2D direct communication has a great advantage in view of efficiency of radio resources because of using relatively fewer radio resources. Additionally, since a method for finding neighboring devices is supported, a device can directly provide necessary information to any desired device, thus enhancing efficiency in supporting an advertisement service, a social networking service (SNS), and the like. Currently, the long term evolution-advanced (LTE-A) system is also requiring a support for D2D technology and therefore brings about a technical discussion.
Recently, an active discussion about a D2D service in the cellular system is in progress, and a discovery between devices is an essential process in the D2D service. In this D2D communication, a method and apparatus for communicating with a device located outside a cellular region are required.